On Blood-Platelets. 



463 



At death these animals exhibited signs of a generalised infection with 

 micro-organisms accompanied by a bronchopneumonia or an enteritis; in one 

 case xerophthalmia was present. If instead of continuing the exposure for 

 13 days, shorter exposures be given, then an amemia will either not develop 

 or will supervene after varying lengths of time according to the dose and 

 the weight of the animal ; and it is remarkable that so far whenever an 

 animal has developed an anfemia it has invariably died within a few days. 

 This suggests that the anaemia is not directly due to the radiation, but is a 

 secondary effect possibly clue to the invasion of the blood stream by micro- 

 organisms. In view of the similarity between these effects and those 

 described above as resulting from withholding vitamin A, an examination of 

 the platelet content of the blood was made to discover whether this could be 

 the primary change to which the invasion of the blood stream by micro- 

 organisms and the -anaemia was secondary. The findings are given in the 

 following protocol. 



Protocol No. 3. 



Five rats : weights 60, 60, 65, 70, 90 grm., exposed as in Protocol No. 1 for 

 5 days, equivalent to 0"46 rads. 



The red cell and haemoglobin content remained normal in every case. 



HOO-, 



Fic. 5. — Effect of radiation on the number of platelets in five rats. Eapid diminution 

 during and after exposure to radium, followed by rapid recovery. 



